1. Field of the Invention
This invention relates generally to focal plane array (FPA) technology. In particular, the present invention has utility for any spectral band FPA that benefits from the physical separation of the detector array from the readout circuit, e.g., pyroelectric and cryogenically cooled infrared FPAs.
2. Background Art
A hybrid FPA is comprised of an array of detectors and a readout circuit for sensing the photon or thermally generated charge on the detectors. Conventional FPAs use physically contacting interconnects, such as indium bumps, to connect the detector elements to the readout circuit. There are several undesirable consequences of this physical contact.
The indium bumps create a high thermal conductance between the detector and readout substrates which force them to operate at near the same temperature. The substrates must be aligned and bonded (hybridized) in a difficult and low yield process. The indium bump bonds also suffer poor reliability particularly for materials of different thermal expansion coefficients.
Thus, there is a great need for an interconnect for focal plane arrays which does not create a high thermal conductance between the detector and readout substrates. An interconnect for focal plane arrays is also needed which substantially eliminates poor reliability caused by structural failures.